Application of SECM to detect a local electrolyte acidification due to the hydrogen flux desorption from a cathodic charged stainless steel

This work aims to estimate local pH variations of a hydrogen charged sample using Scanning ElectroChemical Microscopy (SECM). For that purpose, the microelectrode is polarized in the cathodic domain, where the proton reduction takes place. An initial calibration suggests that cathodic current of the platinum tip is sensitive to pH variations. Then, this system was applied near the surface of stainless steel previously charged with hydrogen. Coupling this result with the analysis of the uncharged samples at two different pH, it appears that hydrogen desorption induces a local acidification which could explain the increase in dissolution kinetics after hydrogen absorption, which has been reported in many studies.